Efficient molasses utilization for low-molecular-weight poly-γ-glutamic acid production using a novel Bacillus subtilis stain

Background: Poly-gamma-glutamic acid (gamma-PGA) is a biopolymer and has various applications based on its biocompatibility, non-toxicity, and edibility. Low-molecular-weight (Mw)-gamma-PGA has promising applications in agriculture and pharmaceuticals. It is traditionally produced by enzymatic hydrolysis. Cost-effective bioproduction of low-Mw-gamma-PGA is essential for commercial application of gamma-PGA. Results: Bacillus subtilis 242 is a newly isolated low-Mw-gamma-PGA-producing strain. To develop cost-effective production of gamma-PGA using this newly isolated strain, cane molasses and corn steep liquor were used to produce gamma-PGA. The concentration of cane molasses was optimized and 100 g/L cane molasses resulted in high gamma-PGA production. The effects of yeast extract and corn steep liquor on gamma-PGA yield were investigated. High concentration of gamma-PGA was obtained in the medium with corn steep liquor. A concentration of 32.14 g/L gamma-PGA was achieved in fed-batch fermentation, with a productivity of 0.67 g/L/h and a percentage yield (g(gamma-pGA)/g(g)(luta)(mate)) of 106.39%. The Mw of gamma-PGA was 27.99 kDa. Conclusion: This study demonstrated the potential application of B. subtilis 242 for cost-effective production of low-Mw-gamma-PGA from cane molasses.